The present invention relates to apparatus for severing multiple layers of coating or covering materials from a central core such as a conductor of a coaxial cable or an optical fiber. More specifically, the invention relates to improvements in automated machinery for sequentially severing and removing multiple layers of material from a wire or other filamentary member utilizing a cutting blade with a circular cutting edge which orbits the material being cut. The prior art includes many types of apparatus for severing and removing a covering layer from a central, filamentary member, as in the removal of insulation and sheathing from an electrical wire or coaxial cable. Such apparatus typically includes one or more cutter blades which are moved from a position spaced radially outwardly from the position at which the cut is to be made inwardly toward the wire, at least partially through the covering layer. The blade(s) may be moved only in linear, reciprocating motion, as in the apparatus of U.S. Pat. No. 5,445,051, or may be rotated about the axis of the wire as they are moved toward and away from the wire, as in the case of U.S. Pat. Nos. 4,745,828 and 4,993,287, or may be moved in a path which orbits the axis of the wire, as disclosed in U.S. Pat. No. 4,619,164. Typically, after the covering layer is severed, the severed section or slug is stripped from the wire. While some forms of apparatus are designed to cut and strip only a single layer of material from the central core, making only one cut at the same axial length from the end of the workpiece and at the same radial depth in each workpiece, others are programmable to make a series of cuts, each through a distinct layer of covering material, at different axial positions and different radial depths, as in the case of coaxial cable where several, superposed layers of covering material are required to be cut and stripped from a central conductor. It is with this latter type of apparatus, particularly that of aforementioned U.S. Pat. No. 4,619,164 (hereinafter “the '164 patent”), that the present invention is concerned.
Orbital motion is imparted to one or the other of the cutting and the wire positioning members in the '164 patent by a rod which rotates about the axis of a motor output shaft but which is arranged with its own axis at an acute angle to the motor shaft axis. The rod passes through a bearing mounted in a housing for axial adjustment along the rod to selectively change the radius of the circular, orbiting motion of the blade. The bearing housing is affixed directly to the movable (cutting or wire positioning) member, thereby translating the nutational motion of the rod to orbiting motion of the movable member. Although effective for the intended purpose, the design subjects a number of parts to excessive wear, is not particularly compact, and has a good deal of inherent play and inaccuracy. One of the objects of the present invention is to provide novel and improved means for imparting orbital motion to a movable member in apparatus for cutting a coating layer on a wire, fiber, or the like.
The cutting edge is, of course, circular in orbiting cutter apparatus and thus, at any given time, engages the cut layer over a limited portion of its periphery, i.e., on only one side. Also, for relatively thin layers, the blade engages the cut layer for only a small depth. Stripping of a severed slug is normally accomplished by holding the workpiece axially stationary and moving the blade in a direction removing the slug, or by holding the cutter blade stationary and moving the workpiece axially. Obviously, if the blade engages the slug over a small peripheral portion at a small depth, stripping ability is impaired as compared to apparatus using two blades which engage the slug on both sides. Thus, the use of a single, orbiting cutting edge, as in the '164 patent, has the disadvantage of impaired stripping capability in at least some applications. Another object of the invention is to provide apparatus which improves the stripping function in cutting/stripping apparatus having an orbiting cutting blade.
The prior art apparatus, in respect of features usually associated with both orbiting blade and rotating blade cutting/stripping devices, is improved upon by the present invention in a number of other ways. These include ease of blade replacement, adjustability of the position of the axis of the wire guide, reduction of wire end “whip” during orbital blade movement, better gravity disposal of debris from stripping operation, improved bearing and bushing design in several mechanical areas, an improved centering technique for calibration of movable gripping members, and both mechanical and operational improvements in clamping assemblies.
A preferred embodiment of apparatus fulfilling and embodying the foregoing and other objects and advantages will be summarized, as well as disclosed in detail, in the following sections.